<template>
  <div class="camera_outer">
    <van-sticky :offset-top="46">
      <van-cell class="btns">
        <van-button type="primary" @click="getCompetence()">打开摄像头</van-button>
        <van-button type="primary" @click="stopNavigator()">关闭摄像头</van-button>
        <van-button type="primary" @click="setImage()">点击拍照片</van-button>
      </van-cell>

      <p style="text-index:2em;font-size:18px;">
        <slot>
          实现设想，通过调用硬件设备的摄像功能，
          进行人脸识别，通过数据库储存的信息比对，
          验证成功则开门，验证失败则不开门，
          并将人脸信息保存，通知管理员交由人工处理。
        </slot>
      </p>
    </van-sticky>
    <video id="videoCamera" :width="videoWidth" :height="videoHeight" autoplay></video>
    <canvas style="display: none" id="canvasCamera" :width="videoWidth" :height="videoHeight"></canvas>
    <div v-if="imgSrc" class="img_bg_camera">
      <van-row justify="center" gutter="20">
        <van-col span="8" v-for="(item, index) in imgs" :key="index">
          <van-image class="tx_img" width="100" height="100" lazy-load :src="item" />
        </van-col>
      </van-row>
    </div>
  </div>
</template>
<script>
export default {
  data() {
    return {
      videoWidth: 410,
      videoHeight: 400,
      imgSrc: '',
      imgs: [],
      thisCancas: null,
      thisContext: null,
      thisVideo: null,
    }
  },
  mounted() {
    this.getCompetence()
  },
  methods: {
    // 调用权限（打开摄像头功能）
    getCompetence() {
      var _this = this
      this.thisCancas = document.getElementById('canvasCamera')
      this.thisContext = this.thisCancas.getContext('2d')
      this.thisVideo = document.getElementById('videoCamera')
      // 旧版本浏览器可能根本不支持mediaDevices，我们首先设置一个空对象
      if (navigator.mediaDevices === undefined) {
        navigator.mediaDevices = {}
      }
      // 一些浏览器实现了部分mediaDevices，我们不能只分配一个对象
      // 使用getUserMedia，因为它会覆盖现有的属性。
      // 这里，如果缺少getUserMedia属性，就添加它。
      if (navigator.mediaDevices.getUserMedia === undefined) {
        navigator.mediaDevices.getUserMedia = function (constraints) {
          // 首先获取现存的getUserMedia(如果存在)
          var getUserMedia =
            navigator.webkitGetUserMedia ||
            navigator.mozGetUserMedia ||
            navigator.getUserMedia
          // 有些浏览器不支持，会返回错误信息
          // 保持接口一致
          if (!getUserMedia) {
            return Promise.reject(
              new Error('getUserMedia is not implemented in this browser')
            )
          }
          // 否则，使用Promise将调用包装到旧的navigator.getUserMedia
          return new Promise(function (resolve, reject) {
            getUserMedia.call(navigator, constraints, resolve, reject)
          })
        }
      }
      var constraints = {
        audio: false,
        video: {
          width: this.videoWidth,
          height: this.videoHeight,
          transform: 'scaleX(-1)',
        },
      }
      navigator.mediaDevices
        .getUserMedia(constraints)
        .then(function (stream) {
          // 旧的浏览器可能没有srcObject
          if ('srcObject' in _this.thisVideo) {
            _this.thisVideo.srcObject = stream
          } else {
            // 避免在新的浏览器中使用它，因为它正在被弃用。
            _this.thisVideo.src = window.URL.createObjectURL(stream)
          }
          _this.thisVideo.onloadedmetadata = function (e) {
            _this.thisVideo.play()
          }
        })
        .catch((err) => {
          console.log(err)
        })
    },
    //  绘制图片（拍照功能）
    setImage() {
      var _this = this
      // 点击，canvas画图
      _this.thisContext.drawImage(
        _this.thisVideo,
        0,
        0,
        _this.videoWidth,
        _this.videoHeight
      )
      // 获取图片base64链接
      var image = this.thisCancas.toDataURL('image/png')
      _this.imgSrc = image
      _this.imgs.push(image)
      this.$emit('refreshDataList', this.imgSrc)
    },
    // base64转文件
    dataURLtoFile(dataurl, filename) {
      var arr = dataurl.split(',')
      var mime = arr[0].match(/:(.*?);/)[1]
      var bstr = atob(arr[1])
      var n = bstr.length
      var u8arr = new Uint8Array(n)
      while (n--) {
        u8arr[n] = bstr.charCodeAt(n)
      }
      return new File([u8arr], filename, { type: mime })
    },
    // 关闭摄像头
    stopNavigator() {
      this.thisVideo.srcObject.getTracks()[0].stop()
    },
  },
}
</script>
<style lang="scss" scoped>
.camera_outer {
  position: relative;
  clear: both;
  overflow: hidden;
  background-size: 100%;
  margin-top: 50px;
  min-height: 100vh;
  video,
  canvas,
  .tx_img {
    -moz-transform: scaleX(-1);
    -webkit-transform: scaleX(-1);
    -o-transform: scaleX(-1);
    transform: scaleX(-1);
  }
  .btn_camera {
    position: absolute;
    bottom: 4px;
    left: 0;
    right: 0;
    height: 50px;
    background-color: rgba(0, 0, 0, 0.3);
    line-height: 50px;
    text-align: center;
  }
  .bg_r_img {
    position: absolute;
    bottom: 0;
    left: 0;
    right: 0;
    top: 0;
  }
  .img_bg_camera {
    position: relative;
    .img_btn_camera {
      position: absolute;
      bottom: 0;
      left: 0;
      right: 0;
      height: 50px;
      line-height: 50px;
      text-align: center;
      background-color: rgba(0, 0, 0, 0.3);
      color: #ffffff;
      .loding_img {
        width: 50px;
        height: 50px;
      }
    }
  }
}
.btns button {
  margin: 0 5px;
}
</style>
